The invention relates to pneumatic tire rims and particularly to rims designed to assist in strengthening the seating relationship between tires and rims.
Recent concern with vehicle safety has prompted manufacturers of various vehicle associated parts and equipment to alter their products. In order that such products contribute to the overall safety of vehicles, many manufacturers have developed new parts and equipment and/or modified their existing products.
Vehicle pneumatic tires have undergone many recent developments, some of which are related to the overall safety of the vehicle upon which they are utilized. One such development has been the "run-flat" pneumatic tire.
Run-flat pneumatic tires are specially designed tires which, under normal circumstances, function as most other tires, but which, upon sudden or gradual loss of air can continue to adequately function for an extended reasonable period of emergency use without air while in a flattened or partially uninflated condition. Categories of type of run-flat tires vary from structurally simple designs to quite elaborate structural combinations. Exemplary of the more structurally simpler run-flat tire constructions is a type of run-flat tire disclosed in U.S. Pat. No. 3,739,829, while a more elaborate run-flat tire would be exemplified in U.S. Pat. No. 2,040,645.
The structurally simpler run-flat tires basically employ designs allowing the tire to operate while totally uninflated to the extent that the tire sidewalls are bulged axially outwardly. Most of these types of run-flat tires typically terminate their emergency use period (i.e. the period during which they are used without air) by having one or both of their bead portions move axially inwardly along the tire rim, displacing the tire from its proper "seat" upon the rim. Thus, how long some of these tires will operate in an uninflated state largely depends upon how long the bead portions remain seated properly on the tire rim while used during this severe emergency period.
There have been modifications made to rims for the purpose of maintaining the bead portions of tires in their properly seated positions. Exemplary of such rim modifications are shown in U.S. Pat. Nos. 2,427,216; 2,663,061; 3,664,405 and 3,669,174. Most of these modifications have proven unacceptable for use with run-flat tires because they give rise to other problems. In many cases, known rim modifications make mounting and dismounting a difficult and/or more time consuming and laborious task. Also, some of these rim modifications have a destructive effect upon the bead portions seated upon the rim. Further, some rim designs modified to provide positive restraint against bead unseating, are so modified at the expense of rim strength or other important rim properties.